1. Field of the Invention
The present invention relates to a vertical heat processing apparatus for a semiconductor process for performing a heat process on target substrates, such as semiconductor wafers, and also to a method for using the apparatus. The term “semiconductor process” used herein includes various kinds of processes which are performed to manufacture a semiconductor device or a structure having wiring layers, electrodes, and the like to be connected to a semiconductor device, on a target substrate, such as a semiconductor wafer or a glass substrate used for an FPD (Flat Panel Display), e.g., an LCD (Liquid Crystal Display), by forming semiconductor layers, insulating layers, and conductive layers in predetermined patterns on the target substrate.
2. Description of the Related Art
In manufacturing semiconductor devices for constituting semiconductor integrated circuits, a target substrate, such as a semiconductor wafer (made of, e.g., silicon) is subjected to various processes, such as film formation, etching, oxidation, diffusion, reformation, annealing, and natural oxide film removal. Jpn. Pat. Appln. KOKAI Publications No. 2000-26973 and US 2006/0286817 A1 disclose a vertical heat processing apparatus (of the so-called batch type), which performs a heat process on a plurality of semiconductor wafers all together. According to this apparatus, semiconductor wafers are first transferred from a wafer cassette onto a vertical wafer boat and supported thereon at intervals in the vertical direction. The wafer cassette can store, e.g., 25 wafers, while the wafer boat can support 30 to 150 wafers. Then, the wafer boat is loaded into a process container from below, and the process container is airtightly closed. Then, a predetermined heat process is performed, while the process conditions, such as process gas flow rates, process pressures, and process temperatures, are controlled.